Conventionally, fitting devices for fitting a cylindrical label made of a resin film onto a columnar target body such as plastic bottles have been known (refer to Patent Literatures 1 to 5 listed below, for example). In these fitting devices, the cylindrical label is generally supplied in a state in which the label is folded into a sheet shape. The fitting device includes a unit called a label opener that opens the label folded in a sheet-shape into a cylindrical shape.
Many label openers are configured to open the label by holding both sides of the label, which is folded, by suction by means of one or more pairs of suction members provided opposite to each other, and thereafter moving the pair of suction members away from each other.
More specifically, Patent Literature 1 discloses a label opener as illustrated in FIGS. 19 and 20. As illustrated in FIG. 19, many of the conventional label openers 90 include plural pairs of grip arms 94 for sandwiching the label F by suction, that are arranged in the height direction of the label. These pairs of grip arms 94 can be opened and closed with respect to each other.
In this label opener 90, pairs of grip arms 94, among the plural pairs of grip arms 94, that are conducive to label suction can be changed, as appropriate, in accordance with the length in the height direction of the label F which is actually to be opened, such that the label F can be gripped by suction in the vicinity of the upper end and the vicinity of the lower end, even if the length of the label in the height direction varies. In other words, according to this prior art, a total of four portions of the label, including a portion in the vicinity of the upper end of one side, a portion in the vicinity of the lower end of one side, a portion in the vicinity of the upper end of the other side, and a portion in the vicinity of the lower end of the other side, are gripped by suction.
Further, in another conventional art label opener which is disclosed in Patent Literature 2 or the like, two pairs of adsorption members, that are capable of holding both sides of the label by adsorption and are also expandable, are provided in the width direction of the label. Accordingly, with this label opener, the label is held by adsorption at four locations that are spaced apart in the width direction.